The primary goal of the Dose-Response to Exercise in Women Aged 45-75 Years (DREW) is to investigate the effects of different amounts of exercise on both cardiorespiratory fitness and risk factors for cardiovascular disease. Participants will be sedentary, overweight or obese, postmenopausal women who have high normal blood pressure or Stage I hypertension, and thus are at moderately high risk for cardiovascular disease. A total of 450 women (35 percent will be from minority groups) will be randomly assigned to a control group (N=100) or to 1 of 3 exercise groups (N=150 for the lowest exercise dose and 100 each in the two highest exercise groups). Women assigned to the exercise groups will exercise for 6 months at energy expenditures of 4, 8, or 12 kcal/kg per week. These exercises doses represent the consensus public health recommendation for physical activity from recently published guidelines from the U.S. Public Health Service, American Heart Association, and the American College of Sports Medicine (8 kcal/kg per week) and at doses 50 percent below (4 kcal/kg per week) 50 percent above (12 kcal/kg per week) the consensus dose. All women will exercise at 50 percent of VO2 max. The exercise sessions will take place in the laboratory, with individual supervision of each session and strict control of frequency, duration, and intensity. This will provide thorough documentation of the exact amount of exercise completed. Primary outcome measures are VO2 max and resting systolic blood pressure. Other cardiovascular disease risk factors, psychosocial variables, health-related quality of life, body composition, and fat distribution are secondary outcomes. Other secondary analyses will include a focus on the extent to which observed dose-response effects are modified by baseline levels of fitness, ethnicity, risk factors, or age. Assessments will take place at baseline and 6 months. The research will provide information about (1) patterns of change in outcomes produced by each of several exercise doses, (2) whether performing exercise at less than the current consensus dose has any benefit, (3) whether performing more exercise than the consensus dose has greater (or proportionally greater) health benefits, and (4) the characteristics of sedentary women who are most likely to benefit from various exercise doses.